When a sperm cell meets and penetrates an egg, it will fertilize it. At this moment, the genetic make-up is complete, including the sex of the infant. Within about three days after conception, the fertilized egg, which is dividing rapidly into many cells, passes through the fallopian tube into the uterus where it attaches to the uterine wall. The placenta, which will nourish the baby, also begins to form. At 4 wks of development the structures that eventually form the face and neck are becoming evident. The heart and blood vessels continue to develop. And the lungs, stomach, and liver start to develop. A home pregnancy test is now positive. At 8 wks the baby is now about the size of a grape – almost an inch in size. Eyelids and ears are forming and even the tip of the nose is visible. The arms and legs are well formed. The fingers and toes grow longer and more distinct. At 12 wks the fetus measures about two and a half inches and starts to make its own movements. You will start to see the top of the uterus above the pelvic bone. Your doctor may hear the baby’s heartbeat with special instruments. The sex organs of the baby should start to become clear. At 16 wks the fetus now measures about 4.3 to 4.6 inches and weighs about 2.8 ounces. The top of your uterus should be felt about three inches below your belly button. The baby’s eyes can blink and the heart and blood vessels are fully formed. The baby’s fingers and toes should have fingerprints. At 20 wks the baby weighs about 9 ounces and is about six inches long. The uterus should be at the level of the belly button. The baby can suck a thumb, yawn, stretch, and make faces. Soon — if you haven’t already — you’ll feel your baby move, which is called “quickening.” At 20 wks an ultrasound is generally performed for all pregnant women at 20 weeks of gestation. During this ultrasound, the doctor will confirm that the placenta is healthy and attached normally and that your baby is growing properly in the uterus. The baby’s heartbeat and movement of its body, arms, and legs can also be seen on the ultrasound. The gender of the baby can usually be determined. At 24 wks the fetus weighs about 1.4 pounds now. It responds to sounds by moving or increasing its pulse. You may notice jerking motions if it hiccups. With the inner ear fully developed, it may be able to sense being upside down in the womb. At 28 wks the fetus weighs about 2 pounds 6 ounces. It changes position frequently at this point in pregnancy. There’s a good chance of survival if your baby was born prematurely now. Ask your doctor about preterm labor warning signs. Register for birthing classes. Birthing classes prepare you for many aspects of childbirth, including labor and delivery and parenting the newborn. At 32 wks the fetus weighs almost 4 pounds. The baby’s skin has less wrinkles as a layer of fat starts to form under the skin. It will gain up to half its birth weight between now and delivery. Ask your doctor how to do a fetal movement chart. Think about breastfeeding. Soon you may start leaking colostrum from your breasts, a yellowish fluid that precedes milk production. At 36 wks babies differ in size, depending on many factors (such as gender, the number of babies being carried, and size of the parents), so your baby’s overall rate of growth is as important as the actual size. On average, it’s about 12.5 inches and weighs 5.5 pounds. The brain has been developing rapidly. Lungs are nearly fully developed. The head is usually positioned down into the pelvis by now. A pregnancy is considered ‘at term’ once 37 weeks has been completed; baby is ready!